EVALUATION OF THE USE OF VOLCANIC TUFF AND BIOMASS ASH TO REMEDIATE ACID MINE DRAINAGE FROM ALMASU MARE, ROMANIA

The Almasu Mare region from the Southern Apuseni Mountains is one of the main ore mining areas in Romania. Mining caused formation of acid mine drainage (AMD) which degrades river and ground waters in this area. AMDs from the Almasu Mare region have pH=2.65-2.80 and a high content (2 to 100 times higher than the maximum admitted values) of Fe, Mn, Al, Cu, Zn and sulphates. The aim of this study was to investigate AMD remediation using low cost materials that are environmental friendly and have the property of pollutant adsorption, as well as pH neutralization. We used volcanic tuff which is a local and cheap sorbent and contains natural zeolite, and biomass ash which is an alkaline waste produced by biomass power plants.

A synthetic acid drainage with concentration of Fe – 620 mg/L and Zn – 130 mg/L, matching the pH and element composition of acid mine drainage from Almasu Mare were exposed to volcanic tuff (powder and granules) and biomass ash (grounded and ungrounded samples). Batch experiments were done using different quantities of materials (liquid to solid ratio (L/S) – 33, 50 and 100), allowing 22 hrs of reaction time, in order to ensure equilibrium is achieved. Fe and Zn were determined by ICP-OES.

Volcanic tuff was effective for the removal of Fe and Zn, but with an increasing dosing and the best results were obtained for granules: 29% Fe and 32% Zn at L/S=100, with pH=4.07, 41% Fe and 44% Zn at L/S=50, with pH=4.17, 46% Fe and 50% Zn at L/S=33, with pH=5.02. In contrast, biomass ash at L/S ratio 100 could neutralise acid mine drainage up to pH=7.81 and remove 99% of Fe and Zn. The results demonstrate that biomass ashes are more effective than volcanic tuff for neutralization and treatment of acid mine drainage. Future challenges involve the design of a filter which can maximize pollutant removal from AMD, using the tested materials.